package com.wang.sort;

import java.util.Arrays;

//selectionSort  选择排序

public class Demo1_SelectionSort {
    public static void selectionSort(int[] arr){
        if(arr == null || arr.length < 2){
            return;
        }
        //0 ~ n-1
        //1 ~ n-1
        //2 ~ n-1
        for (int i = 0; i < arr.length; i++) {//i - n-1 最小值在哪个位置上
            int minIndex = i;
            for (int j = i+1; j < arr.length ; j++) {// i ~ n-1上找最小值的下标
            minIndex = arr[j] < arr[minIndex] ? j : minIndex;
            }
            swap(arr,i,minIndex);
        }
    }

    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] =temp;
    }
    //构造对数器测试算法是否可执行
    //for test
    public static void comparator(int[] arr){
        Arrays.sort(arr);
    }
    //for test
    public static int[] generateRandomArray(int maxSize, int maxValue){
        //Math.random()    [0,1)
        //Math.random() * N  [0,N)
        //(int)(Math.random() * N) [0,N-1]
        int[] arr = new int[(int)((maxSize+1)*Math.random())];
        for (int i = 0; i < arr.length; i++) {
            //[-N,+N]
            arr[i] = (int)((maxSize+1) * Math.random()) - (int)(maxSize * Math.random());
            //[0,+N]
            //arr[i] = (int)((maxSize+1) * Math.random())
        }
        return arr;
    }
    //for test
    public static int[] copyArray(int[] arr){
        if (arr == null){
            return null;
        }
        int[] res = new int[arr.length];
        for (int i = 0; i < arr.length; i++) {
            res[i] = arr[i];
        }
        return res;
    }
    //for test
    //自定义isEqual方法，判断排序后的两个数组中的内容是否一样
    public static boolean isEqual(int[] arr1,int[] arr2){
        if((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)){
            return false;
        }
        if(arr1 == null && arr2 == null){
            return true;
        }
        if(arr1.length != arr2.length){
            return false;
        }
        for (int i = 0; i < arr1.length; i++) {
            if(arr1[i] != arr2[i]){
                return false;
            }
        }
        return true;
    }
    //for test

    public static void printArray(int[] arr) {
        if(arr == null){
            return;
        }
        for (int i = 0; i < arr.length; i++) {
            System.out.println(arr[i] + "");
        }
            System.out.println();
    }
    //for test
    public static void main(String[] args) {
        int testTime = 50000;
        int maxSize = 100;
        int maxValue = 100;
        boolean succeed = true;
        for (int i = 0; i < testTime; i++) {
            int[] arr1 = generateRandomArray(maxSize, maxValue);
            int[] arr2 = copyArray(arr1);
            selectionSort(arr1);
            comparator(arr2);
            if(!isEqual(arr1,arr2)){
                succeed =false;
                printArray(arr1);
                printArray(arr2);
                break;
            }
        }
        System.out.println(succeed ? "Nice!" : "Fucking fucked!");

        int[] arr = generateRandomArray(maxSize,maxValue);
        printArray(arr);
        selectionSort(arr);
        comparator(arr);
    }

}
